Abstract

BACKGROUNG: Dynamic hyperinflation with increased exercise dyspnea has been reported in patients with pulmonary arterial hypertension (PAH). It is unknown the exact pathophysiology of exercise ventilatory mechanics in these patients aggravating dyspnea. Therefore, we assessed detailed ventilatory and sensory responses to exercise contrasting patients with PAH and matched controls. OBJECTIVE: To investigate the relevance of critical inspiratory reserve volume (IRV) achievement on the magnitude o ...

BACKGROUNG: Dynamic hyperinflation with increased exercise dyspnea has been reported in patients with pulmonary arterial hypertension (PAH). It is unknown the exact pathophysiology of exercise ventilatory mechanics in these patients aggravating dyspnea. Therefore, we assessed detailed ventilatory and sensory responses to exercise contrasting patients with PAH and matched controls. OBJECTIVE: To investigate the relevance of critical inspiratory reserve volume (IRV) achievement on the magnitude of dyspnea perception during exercise in PAH patients compared to matched controls. METHODS: 20 non-smoking patients with PAH, age 37.5 ± 12.1ys, forced expiratory volume in 1 second to forced vital capacity ratio (FEV1/FVC) 0.77 ± 0.04, and mean pulmonary artery pressure by right heart catheterization 50.6 ± 18.1mmHg, and 10 age, sex and body mass index matched healthy controls. Patients and controls performed spirometry, measurement of lung volumes using body plethysmography, maximal respiratory pressures and symptom-limited incremental cycling cardiopulmonary exercise test with serial assessments of inspiratory capacity (IC), airway occlusion pressure during the first 0.1s (P0.1) of tidal volume (VT) and Borg dyspnea score RESULTS: Patients showed lower FEV1, FVC, mid-expiratory flows, and FEV1/FVC compared to controls. Dyspnea and minute-ventilation (vE) were significantly higher in patients for a given work rate and dyspnea persisted more intense even when expressed as a function of vE. Exercise-induced reduction in IC predisposed patients to achieve earlier and at lower workloads a critical inspiratory reserve volume (IRV). At this point, there was a sudden raise in P0.1 (adjusted for VT) and dyspnea perception. CONCLUSIONS: Abnormal ventilatory mechanics add up to the excessive exercise ventilation to aggravate dyspnea perception in patients with PAH. Attainment of a critical IRV at premature workloads lead to neuromechanical dissociation with an inflection point increment in exercise dyspnea. ...